1. The Field of the Invention
The present invention relates to fluid mixing systems and, more specifically, fluid mixing systems that control lateral movement of the impeller and/or drive shaft.
2. The Relevant Technology
The biopharmaceutical industry uses a broad range of mixing systems for a variety of processes such as in the preparation of media and buffers and in the growing, mixing and suspension of cells and microorganisms. Some conventional mixing systems, including bioreactors and fermentors, comprise a flexible bag disposed within a rigid support housing. An impeller is disposed within the flexible bag and is coupled with the drive shaft. Rotation of the drive shaft and impeller facilitates mixing and/or suspension of the fluid contained within flexible bag.
To achieve optimal mixing/suspension, the impeller is typically located near the bottom of the bag. This positioning of the impeller typically necessitates the use of a relatively long drive shaft. As the volume of the bag increases, the length of a drive shaft and/or the speed of rotation of the drive shaft and impeller also typically increase. By increasing the length of the drive shaft and the speed of rotation of the drive shaft and impeller, there is a greater chance that the impeller/drive shaft will laterally walk or be displaced within the bag. Unwanted lateral movement of the impeller can potentially cause a number of problems. For example, lateral movement of the impeller can decrease optimal mixing and/or suspension of the fluid which can damage delicate cells and microorganisms. The lateral movement can also potentially cause the impeller/drive shaft to strike the side of the flexible bag which can rupture the bag and/or damage the impeller. Where the mixing system is part of a bioreactor or fermentor or where the solution otherwise needs to remain sterile, rupturing the bag would result in a complete loss of the product being processed. In addition, lateral movement of the impeller/drive shaft can place unwanted stresses on the mixing system which can cause failure.
Accordingly, what is needed in the art are mixing systems as discussed above wherein lateral movement of the impeller/drive shaft can be controlled.